In traditional OFDM/Orthogonal Frequency Division Multiple Access (OFDMA) systems, one set of OFDM parameters, for example, one Cyclic Prefix (CP) length, one subcarrier spacing, and one Fast Fourier Transform (FFT) size, is supported within one cell. The system informs Mobile Stations (MSs) about its OFDM configuration via a broadcast channel.
However, MSs within one cell may have different mobility conditions, from being static to highly mobile. For each mobility type, there is a set of OFDM parameters that is best suitable.
When an operator or a user wants to select only one subcarrier spacing, the subcarrier spacing should support mobility. Thus, when the single subcarrier spacing is used, the selected subcarrier spacing is much larger than is actually needed for low mobility. Further, the larger subcarrier spacing results in increased overhead due to an enlarged symbol duration.